Scientists say climate change made west Africa heavy rainfall five times more likely

Scientists from the World Weather Attribution group said climate change has made extreme rainfall in west Africa about five times more likely than it was in the late 19th century, after floods in the region killed nearly 100 people last month.

The group said in a study that an intense three-day rainfall event is now about five times more likely in the current climate than in a pre-industrial climate. It said such events, once considered rare, can now be expected every two to four years in the region.

The researchers said human greenhouse gas emissions increased the likelihood of the rains that caused the floods and made them 4% to 23% more intense.

The heaviest rainfall came from June 20 to 22, when widespread and persistent downpours affected coastal areas from Ivory Coast to Nigeria, according to the study. Some cities received more than 140 millimetres, or 5.5 inches, of rain in less than 24 hours, overwhelming drainage systems and causing flash floods.

The study said the floods killed at least 59 people in Ivory Coast, 34 in Ghana and five in Togo.

Researchers said fast-growing coastal cities are especially vulnerable because rapid urbanisation has expanded into flood-prone areas. They called on Gulf of Guinea states to prepare for future extremes by investing in drainage systems, early-warning systems and safer housing.